Electron discharge tube



,193 Y o. L. VAN STEENIS 1,980,936

ELECTRON DISCHARGE TUBE Filed Aug. 8, '1930 INVENTOR 0.L. van STEENIS QTTORNEY Patented Nov. 13, 1934 UNITED STATES ELECTRON DISCHARGE TUBE Otto Ilouis van Steenis, Eindhoven, Netherlands, assignor to Radio Corporation of America, a corporation of Delaware Application August 8, 1930, Serial No. 473,815 In the Netherlands September 25, 1929 3 Claims.

This invention relates to a discharge tube wherein the incandescent cathode is resiliently supported and has a number of parallel-connected sections.

In the usual construction, the parallel sections of the filament have joined to them conductors which are at right angles to their length and which in turn are resiliently supported. In such an arrangement, in which the filament parts are stretched between rigid cross-rods so as to be parallel to each other, there is risk of distortion by heat as the filament parts never expand evenly, and thus the filament may contact with the grid.

According to the invention this disadvantage is obviated by spacing the conductor, which establishes the electrical connection between the filaments parts, from the points at which the filament parts are secured to the springs.

It is thus possible for the filament parts to expand independently of one other and constantly remain in a stretched condition so that they will never contact with the grid.

The springs may be secured to a supporting wire which also constitutes the electrical connection between the filament parts.

In one form of construction the springs have their ends which are turned away from the filament bent over a small metal rod to which their ends are joined. In this case the attachment may be effected by means of a metal strip which passes in the direction of length of the supporting wire and is welded to the supporting wire as well as to the ends of the springs.

In another form of construction the springs have their ends which are turned away from the filament bent over a small rod of insulating material to which they are secured by fusing-in, and at the point of fusing the said ends are sharply doubled over so as to emerge again from the insulating rod, the ends emerging from the insulating rod being mutually joined by a strip of metal. In the latter case the resilient arrangement of the filament parts is perfectly independent of the short-circuiting.

In order that the invention may be clearly understood and readily carried into effect, some embodiments thereof will be described more fully with reference to the accompanying drawing, in which:

Figure 1 is a perspective view of a stem having electrodes mounted on it, the anode being omitted for the sake of clearness.

Figure 2 is a perspective View of the springs on a larger scale.

Figure 3 is a corresponding cross-sectional view of the springs shown in Figure 2.

Figure 4 is a perspective view of a different form of arranging the springs Figure 5 is a cross-sectional view of the latter to form of construction.

Referring to Figure 1, the reentrant stem 2 has mounted on it the supporting wires 3 for the anode and two supporting wires 4 for the grid 5. Upon the wires 3 is supported by means of glass beads 6 the conducting support '7 for the resilient conducting members or springs 8. The filament 9 is suspended from the ends of the spring 8. The filament consists of four hairpin shaped filaments arranged in two groups, and comprising eight sections which are connected in parallel four and four, these two groups each of which forms an M shaped filament being connected in series. The filament parts are held at their lower ends by six supporting wires 10, three of which are intended for one parallel group and three for the second parallel group. The supporting wires 10 are short-circuited three and. three by a pair of conductors 11 above the press, one of the three supporting wires 10 of each group being joined to a leading-in wire 12.

The springs 8 may be of molybdenum steel. In the construction shown in Figures 1, 2, and 3 the conductor '7 establishes the electrical connection between the filament parts, consequently both parallel groups are in series connection. Figures 2 and 3 show that the springs 8 are bent at their rear ends around the cylindrical conductor '7 to which their extreme ends are clamped firmly by means of a metal strip 13, which may be welded or otherwise secured to the conductor 7.

In the construction shown in Figures 4 and 5 the springs are similarly bent around an insulating rod 14, say of glass, into the bottom of which they are fused the ends of the springs being sharply doubled over so as to emerge from the rod. A short-circuiting metal strip 15 may be fitted to the ends of the springs which emerge from the glass rod. Due to the fact that the welds are at some distance from the glass rod, the danger that this rod may crack during the welding operation is avoided.

It is, of course, obvious that the same arrangement of springs may be used at the lower ends of the filament parts. the filament parts at their upper parts directly to the short-circuiting conductor.

I claim:

1. A discharge tube comprising a cathode having a plurality of parallel-connected filament sec- This would permit joining 1 tions, a plurality of springs for supporting the CAD filament sections, said springs having their ends which are turned away from the filament bent over a small rod of insulating material to which they are secured by'fusing-in and at the point of fusing the said ends are sharply doubled over so as to emerge again from the insulating rod, the ends emerging from the rod being mutually joined by a strip of metal.

2. In an electron discharge device, a plurality of hair-pin shaped filaments arranged in two groups, a lead-in conductor connected-to each group, a conducting support, and a plurality of resilient conducting members, each having one end engaging the bight .of one of said filaments and the other end being anchored to said support, whereby the fiow of heating current through the filaments of each and the same group is in the same direction, but in opposite directions in one group with respect to the other group.

3. In an electron discharge tube, a reentrant 'stem having a press, a conductor mounted above and in substantially parallel relation tothe press,

a pair of conductors mounted above and in sub- OTTO LOUIS VAN STEENIS. 

